Paragraph 7
In evaluating the subcriticality of fissile material in its transport configuration, the following shall apply:
The determination of subcriticality for irradiated fissile material may be based on the actual irradiation experience, taking into account significant variations in composition.
For irradiated fissile material of unknown irradiation experience the following assumptions shall be made in determining subcriticality:
If its neutron multiplication decreases with irradiation, the material shall be regarded as unirradiated;
If its neutron multiplication increases with irradiation, the material shall be regarded as irradiated to the point corresponding to the maximum neutron multiplication; and
For unspecified fissile material, such as residues or scrap, whose fissile composition, mass, concentration, moderation ratio or density is not known or cannot be identified, the assumption shall be made in determining subcriticality that each parameter that is not known has the value which gives the maximum neutron multiplication under credible conditions of transport.